The present invention relates to a simulator and, more particularly, to a simulator that emulates RF signals that are used to evaluate the operational response of a RF communication array signal processor.
Array signal processors are used in RF communications systems to determine the location of emitters or possibly for beamforming for cancelling the energy of an interfering transmitter. Array signal processors have various operational responses to determine selected parameters of received RF signals, but all array processors have a common requirement to process signals received from an array of multiple antennas that may be at a fixed location or may be mounted on an aircraft. Many signal processors have at least one operational response that uses the time delay between the signals received from the array of multiple antennas that originated from fixed or mobile transmitters. The time delay between the signals may be used either to determine the received signal's angle of arrival, or to steer, on a dynamic basis, the antenna pattern of the array receiving the signals.
Array signal processors, in order to transition from their design concept to their final deployable product, must undergo evaluation testing which may be expensive and costly, especially if the array signal processor is placed on an aircraft. For example, flight testing needs to be performed in order to properly evaluate an airborne array signal processor. Not only are these flight tests expensive, but also the flight testing does not lend itself to repetitive situations which are necessary in order to properly evaluate the response of the array signal processor. Furthermore, the response of the antenna array associated with array signal processors should be evaluated relative to the positions of transmitters that emit the radiating signal which, in turn, requires that the transmitters be physically located miles away from the array signal processor being evaluated.
The antenna array, normally consisting of four antennas, must also be evaluated to determine its operation in a selected frequency range, for example, between 160-180 MHz. The antenna arrays should be evaluated in an environment of being mounted at a stationary (static) location or evaluated as being movable (dynamic) on, for example, an aircraft that is in motion relative to a fixed location. Not only should the antenna array be evaluated on a static and dynamic basis, but the transmitting devices of the signal array processors should also encounter static and dynamic evaluations.
Furthermore, since the accuracy of the RF simulator will determine the accuracy of the array signal processors under test, the simulator should be evaluated on a periodic basis by calibration equipment. Therefore, it is important that the RF simulator, which generates signals incident on an antenna array, allow itself to be easily calibrated. This process will verify that the correct time delays between antennas are generated. It is desired that an array signal processor for RF communication be provided with a simulator having all of the hereinbefore described features so as to perform a proper evaluation of the communication processor.